Time division multiple access (TDMA) radio communication systems are known to include a plurality of radio transceivers, or base stations, that provide radio communication service to a plurality of subscribers throughout a coverage area. These subscribers, which may be portable communication units or mobile communication units, travel throughout the coverage area and communicate with each other by sending radio frequency (RF) signals to a base station servicing their coverage area. These plurality of coverage areas are typically linked together, via a communication network that may include connections to the public switched telephone network (PSTN), and other non-public communication and signaling equipment. Other communication networks-may be entirely private. The base stations are linked to the communication network via a robust communication link, such as a T1 or T3 commonly carried on copper wires, optical fiber or coaxial links.
An exemplary communication system that is known in the art is shown in FIG. 1. Communication system 100 includes radio transceivers 102, 103, which provide communication service to their respective coverage areas. The radio transceivers 102, 103 are further linked to a communication network 106 via communication links 108, 109. In this manner, multiple radio transceivers with overlapping coverage areas can collectively provide a homogeneous, larger coverage area than an individual and isolated radio transceiver coverage area.
As an example of how radio communication service is provided to a coverage area, a first mobile 110 exchanges RF signals using a wireless communication resource 112. In this manner, radio coverage is provided throughout the coverage area being serviced by radio transceiver 102. Similarly, a second mobile 114 is provided radio communication service by radio transceiver 103 through the exchange of RF signals on wireless communication resource 116. In order to establish a communication path between the first mobile 110 and the second mobile 114--with the first mobile 110 as the requesting mobile for this service--the first mobile 110 exchanges RF signals with its serving radio transceiver 102 to notify and request communication services from the radio transceiver 102 and the communication network 106. In response to this request, the communication network 106 then locates and notifies the second mobile 114 by exchanging information with radio transceiver 103. If the second mobile 114 is available for the requested communication service, an end-to-end communication link is provided between the first mobile 110 and the second mobile 114 through radio links 112, 116, radio transceivers 102, 103, transmission links 108, 109 and the communication network 106.
Digital wireless communication networks that employ time division multiplex access (TDMA) techniques require the transmission and receipt of information over the radio link during a pre-determined time period (hereafter "timeslot"). Timeslots are generally constructed to repeat and become available at regular intervals, and hence radio transceivers and subscriber units can only transmit or receive information over the radio link during a pre-assigned timeslot. This process is commonly referred to as timeslot alignment. Further, the time that information arriving at the radio transceiver (e.g., 102) and destined for a mobile (e.g., 110) must wait (i.e., hold) until the next pre-assigned timeslot occurs is referred to herein as the "hold time", denoted T.sub.H, as later described with reference to FIG. 2.
Each component in a digital wireless communication system (e.g., subscriber equipment, radio transceivers and communication network) exhibit a certain amount of processing delay, denoted T.sub.P, i.e., the time required to process incoming and outgoing information. Additionally, the transmission links 108 and 109, as well as the communication network 106, present a certain amount of delay to propagating information, referred to herein as "network delay", and denoted T.sub.N. It is well understood that audio delay is an inherent property of digital TDMA wireless communication systems and is primarily caused by the network delays, processing delay and hold time in the system.
Accordingly, a need exists for a TDMA based radio communication system that is not constrained by the shortcomings of the prior art. In particular, a signaling method that reduced the audio delays experienced during mobile to mobile communications would be an improvement over the prior art.